iTHEMS Weekly News Letter

Event Schedule

Events for the 2nd week of April 2021


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Research News

RIKEN RESEARCH: Supernova simulations reveal how stellar explosions shape debris clouds thumbnail

RIKEN RESEARCH: Supernova simulations reveal how stellar explosions shape debris clouds


Astronomers are now in a better position to interpret observations of supernova remnants thanks to computer simulations of these cataclysmic events by RIKEN astrophysicists.

Hot Topic

Seminar Report

Biology Seminar by Dr. José Gutiérrez on March 25, 2021


On March 25th, José Gutiérrez from Chiba University gave a talk at iTHEMS Biology Seminar about the evolution and diversification of cycads ("sotetsu" in Japanese) in Mexico. He explained how the different species and populations of cycads are distributed in different areas of Mexico, and showed how this can be explained by changes in the climate and the adaptation of each species to the different environment. He then discussed some general ideas of how speciation and diversification can occur. It was probably the first time for many iTHEMS members to hear about research in Ecology, and I think many of us learned something new. We were also able to have a nice and fruitful discussion after the talk.

Reported by Jeffrey Fawcett

Seminar Report

Biology Seminar by Dr. Yuji Hirono on April 1st, 2021


In iTHEMS biology seminar on April 1st, Yuji Hirono (Assistant Professor, Asia Pacific Center for Theoretical Physics, POSTECH, Korea) gave us a talk on chemical reaction networks. Hirono-san has been recently working on chemical reaction networks with Miyazaki-san, Hidaka-san, and me. In the seminar, he talked about a new method of studying chemical reaction networks from network topology. He first explained graph theoretical aspects of chemical reaction systems, and then explained how these tools can be used to characterize reaction systems. Then, he explained a method of simplifying/deforming chemical reaction systems without affecting steady-state properties. I am grateful to Hirono-san because I could improve my understanding of reaction systems through collaboration with him. Also, Hirono-san and I have been friends since we were undergraduates, and I am happy to work together. Thank you very much, Hirono-san!

Reported by Takashi Okada

Upcoming Events


iTHEMS Math Seminar

Long-time behavior of moving solids in a fluid and the kinetic theory of gases

April 7 at 16:00 - 18:10, 2021

Dr. Kai Koike (JSPS Fellow, Graduate School of Engineering, Kyoto University)

Understanding dynamics of solids in a fluid is a fundamental problem in fluid dynamics. Due to the growing interest in engineering in out-of-equilibrium situations, moving boundary problems for kinetic equations such as the Boltzmann equation have become an active area of research.

In the first part of the talk, I shall explain recent, especially mathematical, developments in this field. Then in the second part, I'd like to explain my results concerning the long-time behavior of a point particle moving in a 1D viscous compressible fluid. These results aim to give some explanation of related numerical simulations for a BGK model of the Boltzmann equation.

Venue: via Zoom

Event Official Language: English


Math-Phys Joint Seminar

Self-adjoint extension in quantum mechanics and non-Rydberg spectra of one-dimensional hydrogen atom

April 13 at 16:00 - 18:10, 2021

Prof. Takuju Zen (Professor, School of Environmental Science and Engineering, Kochi University of Technology)

We offer a beginner’s guide to the functional-analytical techniques in quantum mechanics, and cover its application to the 1D Coulomb problem. It is shown that the wave function at the diverging point of the Coulomb potential is mathematically described by three-parameter family of generalized connection conditions. A scheme is devised to physically implement the generalized conditions, which provides the way to experimentally realize non-Rydberg spectra in 1D Hydrogen atom.

Part 1, Self-adjoint extension of Hilbert space operator
Part 2, 1D Coulomb problem

Venue: via Zoom

Event Official Language: English


iTHEMS Colloquium

Mirror symmetry and KAM theory

April 16 at 13:30 - 15:00, 2021

Prof. Kenji Fukaya (Permanent Member, Simons Center for Geometry and Physics, Stony Brook University, New York, USA)

13:30pm-15:00pm (JST)

Mirror symmetry is a phenomenon discovered in String theory and is much discussed recently in mathematics especially in the field of complex (algebraic) geometry and symplectic geometry. Strominger-Yau-Zaslow found that this phenomenon is closed related to a Lagrangian torus fibration. In an integrable system in Hamiltonian dynamics, the phase space is foliated by Lagrangian tori. I would like to explain a program that the Lagrangian torus fibration found by Strominger-Yau-Zaslow could be regarded as one appearing certain integrable system and KAM theory (which describes a amiltonian dynamics that is a perturbation of an integrable system) could appear in the situation of Mirror symmetry.

Venue: via Zoom

Event Official Language: English


The 15th MACS Colloquium thumbnail

MACS ColloquiumSupported by iTHEMSSUURI-COOL (Kyoto)

The 15th MACS Colloquium

April 23 at 15:00 - 17:30, 2021

Prof. Hiroshi Ishikawa (Professor, Faculty of Science and Engineering, Waseda University)

15:00- Talk by Prof. Hiroshi Ishikawa
16:05- MACS Student Conference FY2021

Venue: via Zoom

Event Official Language: Japanese

Paper of the Week

Week 1 of April 2021


Sorry for not being updated since February due to a system error.

Title: Impacts of new small-scale N-body simulations on dark matter annihilations constrained from cosmological 21cm line observations
Author: Nagisa Hiroshima, Kazunori Kohri, Toyokazu Sekiguchi, Ryuichi Takahashi

Title: Quantifying the relative contribution of free virus and cell-to-cell transmission routes to the propagation of hepatitis C virus infections in vitro using an agent-based model
Author: Kenneth Blahut, Christian Quirouette, Jordan J. Feld, Shingo Iwami, Catherine A. A. Beauchemin

Title: Arithmetic and geometric deformations of $F$-pure and $F$-regular singularities
Author: Kenta Sato, Shunsuke Takagi

Title: Codimension 2 transfer of higher index invariants
Author: Yosuke Kubota

Title: Dynamic sampling bias and overdispersion induced by skewed offspring distributions
Author: Takashi Okada, Oskar Hallatschek

Title: Dual Labor Market and the "Phillips Curve Puzzle"
Author: Hideaki Aoyama, Corrado Di Guilmi, Yoshi Fujiwara, Hiroshi Yoshikawa

Title: Dirac Fermion Cloning, Moiré Flat Bands and Magic Lattice Constants in Epitaxial Monolayer Graphene
Author: Qiangsheng Lu, Ching-Kai Chiu, Congcong Le, Jacob Cook, Xiaoqian Zhang, Xiaoqing He, Mohammad Zarenia, Mitchel Vaninger, Paul F. Miceli, Chang Liu, Tai-Chang Chiang, Giovanni Vignale, Guang Bian

Title: Functional-renormalization-group approach to classical liquids with short-range repulsion: a scheme without repulsive reference system
Author: Takeru Yokota, Jun Haruyama, Osamu Sugino

Title: The bulk-dislocation correspondence for weak topological insulators on screw-dislocated lattices
Author: Yosuke Kubota

Title: Structural reduction of chemical reaction networks based on topology
Author: Yuji Hirono, Takashi Okada, Hiroyasu Miyazaki, Yoshimasa Hidaka

Title: Optical Spin Transport in Ultracold Quantum Gases
Author: Yuta Sekino, Hiroyuki Tajima, Shun Uchino

Title: Improving Schrödinger Equation Implementations with Gray Code for Adiabatic Quantum Computers
Author: Chia Cheng Chang, Kenneth S. McElvain, Ermal Rrapaj, Yantao Wu

Title: Diagnosis of information scrambling from Hamiltonian evolution under decoherence
Author: Tomoya Hayata, Yoshimasa Hidaka, Yuta Kikuchi

Title: Nuclear energy density functionals from empirical ground-state densities
Author: Giacomo Accorto, Tomoya Naito, Haozhao Liang, Tamara Niksic, Dario Vretenar

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